I can not speak to the type or quality of metal they are made of with 100% certainty, but they do not appear to be made of Zinc. All the written material I have seen says they are steel. So far all the written material specs on the Hooben Sherman have proven correct. Regardless of the metal used be it some unknown quality of steel or a Zinc alloy, this testing aims to find what kind of longevity the parts have. Given the type of abuse and extended running times this tank is seeing we should know soon enough if these gearboxes will last. At this point these gearboxes have seen at least 10 hard hours of run time since the start of this review.

Side note: I am actually more concerned that the tracks or sprockets will fail long before there are any issues with the gearboxes. The Gearboxes in my opinion are overbuilt for this tank and a simpler 3:1 or 4:1 design would have been just as good and possibly brought the retail price down a bit. Plus it would have made for easier customization.

Sorry that was a rather long winded responce to a simple question.